Li Liangbin, Meng Fenghua, Zhong Zhiyuan, Byelov Dmytro, de Jeu Wim H, Feijen Jan
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Anhui 230026, China.
J Chem Phys. 2007 Jan 14;126(2):024904. doi: 10.1063/1.2405357.
The morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) (PCL-b-PEO) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy. The molecular masses Mn of the PCL and PEO blocks are 24,000 and 5800, respectively. X-ray scattering and rheological measurements indicate that no microphase separation occurs in the melt. Decreasing the temperature simultaneously triggers off a crystallization of PCL and microphase separation between the PCL and PEO blocks. Coupling and competition between microphase separation and crystallization results in a morphology of PEO spheres surrounded by PCL partially crystallized in lamella. Further decreasing temperature induces the crystallization of PEO spheres, which have a preferred orientation due to the confinements from hard PCL crystalline lamella and from soft amorphous PCL segments in different sides. The final morphology of this highly asymmetric block copolymer is similar to the granular morphology reported for syndiotactic polypropylene and other (co-) polymers. This implies a similar underlying mechanism of coupling and competition of various phase transitions, which is worth further exploration.
采用原位同时小角和广角X射线散射以及原子力显微镜研究了一种高度不对称的双可结晶聚（ε-己内酯-b-环氧乙烷）（PCL-b-PEO）嵌段共聚物的形态。PCL和PEO嵌段的分子量Mn分别为24000和5800。X射线散射和流变学测量表明，熔体中未发生微相分离。降低温度同时引发PCL的结晶以及PCL和PEO嵌段之间的微相分离。微相分离和结晶之间的耦合与竞争导致了PEO球被部分以片晶形式结晶的PCL包围的形态。进一步降低温度会诱导PEO球的结晶，由于来自不同侧的硬PCL结晶片晶和软无定形PCL链段的限制，PEO球具有择优取向。这种高度不对称嵌段共聚物的最终形态类似于间规聚丙烯和其他（共）聚物所报道的颗粒形态。这意味着各种相变的耦合与竞争存在类似的潜在机制，值得进一步探索。
